Known methods for the manufacture of self-ventilating braking bands of composite material can be divided generally into three groups.
The first group of known methods provides for the moulding of the braking band as a solid body similar to that of a non-ventilated brake disk and the subsequent formation of radial and non-radial holes lying in the central plane of the thickness of the band and constituting the ventilation ducts.
The second group of methods for the production of self-ventilated braking bands of composite material provides, in a first step, for the separate moulding of two reflectively symmetrical portions of the braking band, which have channels in their respective surfaces that face one another. The two portions are then brought into contact and glued together to form the finished band in which the channels of each of the portions together define the ventilation ducts.
In the third group of known methods, the ventilation ducts are produced by means of a core of composite material which is inserted in the mould, between two layers of the material for forming the band, and which already has in its interior the cavities which will constitute the ventilation ducts. Since it is made of material identical or at least similar to that of the band, the core becomes closely connected to the composite material of the braking band, forming a composite “sandwich” structure therewith. The core itself is formed by two half-cores arranged facing one another and glued together in a similar manner to the braking band of the above-mentioned second production method.
However, the above-mentioned methods of the prior art have some problems and disadvantages connected mainly with technological difficulties.
In the first method, the formation of the holes in the thickness of the braking bands is without doubt very expensive and difficult because of the hardness of the materials used. Moreover, this machining inside the braking band is much less controllable than the machining of the outer surfaces of the band. During this machining, it is consequently not possible to exclude the formation of sharp edges or even cracks, which cannot be tolerated in view of the intrinsic fragility of the materials used.
The second method, on the other hand, has the great disadvantage of the need to join together two portions of a braking band which, since they are moulded separately, may not correspond and may therefore fit together unevenly. This could give rise to a product in which dangerous detachment of these two portions can easily occur.
With regard to the third group of known methods, this requires the provision of two moulds for the moulding of the respective half-cores, as well as a third mould for the moulding of the braking band. Moreover, in order to achieve satisfactory results, the core produced by means of the two half-cores has to be positioned very accurately inside the mould for the braking band. All of this requires quite complex technical solutions as well as manual intervention in every moulding cycle.
The above-mentioned technological difficulties, as well as the resulting costs, also reduce the competitiveness of self-ventilated brake disks made of composite material, in comparison with solid disks.
There is consequently a need to provide tools and a method for the production of self-ventilated braking bands of composite material which are particularly simple and which ensure a product of optimal quality, as well as to provide braking bands produced by means of these tools and this method.
The proposed aim of the present invention is therefore to devise a mould for the production of self-ventilated braking bands of composite material such as to satisfy the above-mentioned needs and at the same time to overcome the disadvantages mentioned with reference to the prior art.